1. Field of the Invention
The present invention relates to a relay station device, a base station device, a mobile station device, and a radio communication system. More specifically, the present invention relates to, in a cellular system in which a mobile station device connects wirelessly to a network via a base station device, a communication methodology for the mobile station device to communicate not only with the base station device, but also with a relay station device which is connected wirelessly to the base station device.
2. Description of the Related Art
In a cellular radio communication system (hereinafter, may be simply referred to as “radio communication system”), there is a case where a relay station device (hereinafter, may be simply referred to as “relay station”) is installed for the purpose of extending a service area covered by a base station device (hereinafter, may be simply referred to as “base station”). The base station connects to and provides a communication path to any mobile station device (hereinafter, may be simply referred to as “mobile station”), and the base station also connects to and provides a communication path to the relay station. The relay station further connects to and provides a communication path to another mobile station. In such configuration, the mobile station can communicate with the base station via the relay station. In this way, even when the mobile station is located outside a service area within which a service is provided by the base station, the mobile station can perform communication as long as the mobile station is located within a service area covered by the relay station.
As for a radio communication system including a relay station, there is disclosed, for example, a methodology for reducing the burden on the relay station (e.g., see JP-A-2008-118659). Further, for example, in order to reduce the processing performed in the relay station, there are disclosed techniques for adjusting a timing of a base station transmitting data to a relay station, taking into consideration the occurrence of a time lag in performing data transmission from the relay station to a mobile station (e.g., see JP-A-2008-48218 and JP-A-2008-109374).
Further, as for a channel allocation control method in a radio communication system including a relay station, there is disclosed a method of controlling the allocation of channels on the basis of a total average data rate (e.g., see JP-A-2008-48416). In addition, as for an operation method of an antenna pattern in a radio communication system including a relay station, there is disclosed a method for accelerating link establishment by switching array antennas (e.g., see JP-A-2008-48236).
When a service area can be expanded by installing a relay station in addition to a base station, it becomes possible for service providers to create a radio communication system with less investment.